The U.S. Federal Trade Commission's antitrust investigation into Google's search engine could shine some light on the secret inner workings of the company's search ranking decisions and the relationship between advertising and free search results, some Google critics said Friday.

With other Google services being integrated with its search engine and Google offering both paid search and free search results, there's an "enormous possibility for abuse," said Eric Clemons, an operations and information management professor at the University of Pennsylvania.

Google's paid search service gives the company an incentive to keep its free search results from getting too good, Clemons said at a Technology Policy Institute (TPI) forum on Google and antitrust in Washington, D.C. "I've always wanted to say this in Washington: Follow the money," he said.

The FTC's antitrust probe of Google, reported in June, will give investigators a chance to see how Google ranks search results, giving the public a "first line of defense" against anticompetitive practices, said Oren Bracha, a law professor focused on technology and intellectual property at the University of Texas.

"The whole search process is shrouded in secrecy," Bracha said. "It's a big black box, and nobody except Google really knows what's going on in there. Somebody gets to open the black box."

While Clemons and Bracha argued in favor of an investigation, other speakers on Friday questioned whether an antitrust probe of Google was appropriate. Though some competitors have complained about Google's search dominance and its search rankings, antitrust cases must show harm to consumers, said Geoffrey Manne, founder of the International Center for Law and Economics, an organization that has received support from Google.

There don't seem to be any major complaints against Google alleging consumer harm, Manne said.

Also, although Google has become a huge company, that's not a good reason to bring an antitrust lawsuit against the company, said Manne and Michael Katz, a business professor at the University of California, Berkeley. U.S. law allows companies to become monopolies, as long as they act fairly, said Katz, who has worked with Google.

"In the United States, there's nothing wrong with making lots of money," Katz said.

Google should have the ability to add services and integrate search functionality with other products as a way to better serve customers, Katz said. Microsoft's Bing search engine integrates an airfare pricing service, and there are few complaints, he said.

People complaining about Google adding services to search have the attitude of, "Innovation? We don't need no stinkin' innovation," Katz said.

Thomas Lenard, TPI's president, questioned how FTC investigators could tell if Google's search results were biased. "If you were at the FTC, what would you be looking at?" he said.

Determining search bias will not be easy, Bracha said. "One cannot imagine equal, neutral treatment for everybody in this context," he said. "Search, in order to be useful at all, is inherently hierarchical. Somebody has to be at the bottom."

But the American Homeowners Grassroots Alliance, an advocacy group that doesn't disclose its supporters, has heard "countless complaints" from small-business marketers of niche products who see their Google search rankings drop for no apparent reason, said Bruce Hahn, the group's president.

"I don't know what other explanation there could be, other than there's some bias in Google search, and for what reasons, other than financial gain?" Hahn said.

Friday's Google antitrust forum may be a preview of a U.S. Senate hearing next Wednesday. The Senate Judiciary Committee's antitrust subcommittee will host a hearing entitled, "The Power of Google: Serving Consumers or Threatening Competition?" at 2 p.m. that day. Eric Schmidt, Google's executive chairman, is scheduled to be a witness.

Grant Gross covers technology and telecom policy in the U.S. government for The IDG News Service. Follow Grant on Twitter at GrantGross. Grant's e-mail address is grant_gross@idg.com.